Thermo-Reversibility and Crack-Healing of A Cross-Linked Maleimide/furan Polymer

Polymers are widely used in areas such as composites, marine, aerospace and car industry, being irreversibly damaged by high stresses. The research's objective is characterizing the thermo-rheological properties of a new cross-linked polymeric structure, which can potentially be crack-healed multiple times by forming new covalent bonds. A re-mendable maleimide/furan cross-linked polymer was synthesized through Diels-Alder thermo-reversible reaction between 1,1?(methylenedi-4,1-phenylene) bismaleimide: multi-functional dienophile, and pentaerythritol propoxylate tris(3-(furfurylthio)propionate): multi-functional diene, then cured without solvent at 145°C (agitation) for 30 minutes showing a fast chemical equilibrium with unique consistency in mechanical properties. Multi-functional furan was synthesized through Michael's addition of pentaerythritol propoxylate triacrylate and furfuryl mercaptan obtaining a pure product (C-NMR) by evaporation of unreacted thiol. It can transition from a glassy to a liquid state from ~85°C to ~103°C. It follows the theory of cross-linked polymers scaling and has a gel point at 95°C indicated by Winters-Chambon criteria. It follows in a very particular way the Law of Rubber Visco-elasticity with inverse relation between the storage and the loss modulus to temperature. Thermo-reversibility allows cross-link density and hence modulus manipulation. Chemical equilibria and cross-link density are being studied. Findings could be applied to other systems, developing new crack-healing polymers with different applications.